The goal of the proposed project is to characterize the memory representations and operations that enable successful comprehension of language in real-time. Understanding written and spoken language routinely requires readers and listeners to establish dependencies between sentential elements that span several words, phrases, or even clauses. To fully integrate new information into an evolving interpretation of the discourse, comprehenders must gain access to the memory representations associated with earlier parts of the text or utterance. Despite the centrality of memory to comprehension, research has not clearly identified (a) when information must be retrieved from memory for comprehension to be successful, (b) how information is retrieved from memory, and (c) what factors determine the success of retrieval. These questions form the core of this project, and we propose to address them with conventional eye-tracking procedures during reading and with speed-accuracy tradeoff (SAT) procedures. The use of SAT is a unique aspect of this proposal. The method has been widely used to gain information about memory and attention processing, and its application in the realm of sentence processing will enable precise measurements of how the interpretations of different sentence structures unfold over time, as well as tests of hypotheses that cannot be evaluated with conventional measures alone. Building on basic memory research and preliminary findings in comprehension, the project addresses the following hypotheses: (a) Retrieval from memory is required whenever on-going processing displaces representations from a very limited focus of attention. We will investigate the effective span of focal attention in comprehension, and whether it interacts with linguistic structure and linguistic devices for focusing information. (b) Different models for how retrieval operates have been proposed. We test these models, and specifically investigate the hypothesis that representations formed during comprehension are content-addressable and retrieved with a direct-access operation. (c) Interference is a major determinant of retrieval failures. We explore the hypothesis that retrieval interference is a significant determinant of successful comprehension, and that it may determine the limits on our ability to interpret complex sentence structures. PUBLIC HEALTH RELEVANCE: The memory mechanisms that we propose to investigate in this project comprise the basic building blocks necessary for skilled language and reading comprehension. We anticipate that the project will provide benchmark data on attentional span, the nature of retrieval, and the role of interference in comprehension in normal populations. The project will provide a detailed and comprehensive foundation for future investigations of developmental changes, individual differences, and abnormalities within the comprehension system.